Expansion lock



FIG. 1 is a front elevational view of an expansion bolt showing my new design;

FIG. 2 is a side elevational view taken from the right of FIG. 1;

FIG. 3 is a rear elevational view;

FIG. 4 is a side elevational view taken from the left of FIG. 1;

FIG. 5 is a top plan view;

FIG. 6 is a bottom plan view. 

The ornamental design for an expansion lock, substantially as shown and described. 